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Pluto is a dwarf planet placed in the Kuiper belt a doughnut-shaped region of icy bodies beyond the orbit of Neptune. Discovered in 1930, Pluto has long been considered the ninth planet of our Solar System. However, after the discovery of similar worlds in the Kuiper belt, it has been reclassified as dwarf planet. Pluto is smaller than the Moon, and lies about 5,8 billions km from the Sun. It has a thin atmosphere, mainly composed of nitrogen, methane and carbon monoxide. On average, the temperature of Pluto is -232°C, andLEGGI TUTTO